Background:Pulsed radiofrequency (PRF) application to the dorsal root ganglia can reduce neuropathic pain (NP) in animal models,but the effect of PRF on damaged peripheral nerves has not been examined.We investigated the effect of PRF to the rat sciatic nerve (SN) on pain-related behavior and SN ultrastructure following chronic constriction injury (CCI).Methods:The analgesic effect was measured by hindpaw mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL).Twenty rats with NP induced by ligating the common SN were then randomly divided into a PRF treatment group and a sham group.The contralateral SN served as a control.The MWT and TWL were determined again 2,4,6,8,10,12,and 14 days after the PRF or sham treatment.On day 14,ipsilateral and contralateral common SNs were excised and examined by electron microscopy.Results:Ipsilateral MWT was significantly reduced and TWL significantly shorter compared to the contralateral side 14 days after CCI (both P =0.000).In the PRF group,MWT was significantly higher and TWL significantly longer 14 days after the PRF treatment compared to before PRF treatment (both P =0.000),while no such difference was observed in the sham group (P ＞ 0.05).Electron microscopy revealed extensive demyelination and collagen fiber formation in the ipsilateral SN of sham-treated rats but sparse demyelination and some nerve fiber regrowth in the PRF treatment group.Conclusions:Hyperalgesia is relieved,and ultrastructural damage ameliorated after direct PRF treatment to the SN in the CCI rat model of NP.